Improved smoothing of an altimetric ocean-tide model with global Proudman functions

Abstract. The tides for the Mediterranean Sea are described through a high resolution model (MEDI10) developed by assimilation of tide-gauge data and T/P data into a barotropic ocean tide model. Tidal parameters from 56 coastal tide-gauge stations around the Mediterranean for eight principal constituents: M2, S2, N2, K2, K1, O1, P1 and Q1 and from 20 stations for M2, S2, K1, O1 are included in the model. TOPEX/Poseidon data with all corrections applied except for the ocean tides and bathymetry from TOPO 13.1 were used for development of the model. Numerical experiments were carried out for the estimation of the friction velocity and of the decorrelation length scale. The experiments related to the friction velocity showed that the use of spatially varying friction velocity, estimated as a function of position in the model domain, gives better results than a constant value. The experiments related to the estimation of the decorrelation length suggest that the results are not sensitive for lengths close to ten times the length of the grid cell. The assessment of the model is based on ten tide-gauge observations that are not used for the assimilation. Comparisons were carried out with contemporary published global or regional models. The final solution is computed using 76 selected coastal tide-gauge stations. The comparison between the observed and the model constituents results in a Root Sum of Squares (RSS) equal to 1.3 cm.

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Impact of the stochastic model of the ocean tides on GRACE monthly gravity field solutions

10.5194/egusphere-egu21-15292 ◽

2021 ◽

Author(s):

Natalia Panafidina ◽

Rolf Koenig ◽

Karl Neumayer ◽

Christoph Dahle ◽

Frank Flechtner

Keyword(s):

Gravity Field ◽

Spherical Harmonics ◽

Research Unit ◽

Ocean Tide ◽

Model Errors ◽

Ocean Tides ◽

Tidal Waves ◽

Ocean Tide Model ◽

Tide Model ◽

Grace Data

In GRACE data processing the geophysical background models, which are needed to compute the monthly gravity field solutions, usually enter as error-free. This means that model errors could influence and distort the gravity field solution.The geophysical models which influence the solution the most are the atmosphere and ocean dealiasing product (AOD1B) and the ocean tide model. In this presentation we focus on the ocean tide model and on incorporating its stochastic information in data processing. We use the FES2014 ocean tide model presented as a spherical harmonic expansion till degree and order 180. The information about its uncertainties and the correlations between different spherical harmonics is provided by the research unit NEROGRAV (New Refined Observations of Climate Change from Spaceborne Gravity Missions). In a first step, the stochastic properties of the tide model are considered to be static and are expressed as variance-covariance matrices (VCM) of the spherical harmonics of the 8 main tidal waves till degree and order 30. The incorporation of this stochastic information is done by setting up the respective ocean tide harmonics as parameters to be solved for. Since ocean tides cannot be freely estimated within monthly GRACE solutions, the provided VCMs for the 8 tidal waves are used for constraining the tidal parameters.This procedure was used to compute monthly gravity field solutions for the year 2007. For a comparison, we computed also monthly gravity fields without taking into account the stochastic information on ocean tides. In this contibution we present and discuss the first results of this comparison.

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Research Article. Towards a tidal loading model for the Argentine-German Geodetic Observatory (La Plata)

Journal of Geodetic Science ◽

10.1515/jogs-2017-0002 ◽

2017 ◽

Vol 7 (1) ◽

Author(s):

A. Richter ◽

L. Müller ◽

E. Marderwald ◽

L. Mendoza ◽

E. Kruse ◽

...

Keyword(s):

Earth Tides ◽

Global Ocean ◽

Ocean Tide ◽

Observation Data ◽

Additional Contribution ◽

La Plata ◽

Ocean Tide Model ◽

Tide Model ◽

Loading Effects ◽

Tidal Loading

AbstractWe present a regionalized model of ocean tidal loading effects for the Argentine-German Geodetic Observatory in La Plata. It provides the amplitudes and phases of gravity variations and vertical deformation for nine tidal constituents to be applied as corrections to the observatory’s future geodetic observation data. This model combines a global ocean tide model with a model of the tides in the Río de la Plata estuary. A comparison with conventional predictions based only on the global ocean tide model reveals the importance of the incorporation of the regional tide model. Tidal loading at the observatory is dominated by the tides in the Atlantic Ocean. An additional contribution of local tidal loading in channels and groundwater is examined. The magnitude of the tidal loading is also reviewed in the context of the effects of solid earth tides, atmospheric loading and non-tidal loads.

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